It is known that, by the color development of a silver halide color photographic material, an oxidized aromatic primary amine developing agent can react with a coupler to form a dye such as an indophenol, an indoaniline, an indamine, an azomethine, a phenoxazine, a quinoneimine, a phenazine, and the like, thus forming a color image (for example, refer to T. H. James, The Theory of the Photographic Process, 3rd Edition, pages 382 to 396, Macmillan Co., New York (1971)). In this procedure, the subtractive color process is ordinarily used for color reproduction, and silver halide emulsions which are selectively sensitive to blue, green, and red lights, and yellow, magenta, and cyan color image formers, which are respectively the complementary colors of blue, green, and red, are employed. For example, a coupler of the acylacetanilide, malondianilide or dibenzoylmethane type is used for forming a yellow color image; a coupler of the pyrazolone, pyrazolobenzimidazole, cyanoacetophenone, pyrazolotriazole or indazolone type is generally used for forming a magenta color image; and a phenolic coupler, such as a phenol and a naphthol, is used for forming a cyan color image.
Color photographic light-sensitive materials are roughly divided into two classes, one of which is a coupler-in-developer type color photographic light-sensitive material wherein a coupler is added to a developing solution, and the other of which is a coupler-in-emulsion type color photographic light-sensitive material wherein a coupler is incorporated into each light-sensitive layer of the photographic material so as to maintain the independent function thereof. In the latter photographic material a dye image forming coupler is added to a silver halide emulsion layer. It is required that a coupler added to an emulsion layer be rendered nondiffusible (diffusion-resistant) in a binder matrix of the emulsion layer.
On the other hand, 2-equivalent couplers in which a group capable of being released upon the coupling reaction with an oxidized product of a developing agent is substituted at the coupling position thereof are also known. A 2-equivalent coupler can form 1 mole of dye using 2 moles of silver, although at least 4 moles of silver are required by a 4-equivalent coupler in order to form 1 mole of dye. Therefore, it is possible to reduce the amount of silver coated in the photographic light-sensitive material by employing a 2-equivalent coupler, resulting in a decrease in production costs and a reduction in the film thickness.
Although 2-equivalent couplers are known having satisfactory characteristics, it has still been desired to improve their properties. In particular, many known 2-equivalent couplers are insufficient with respect to color forming properties in high temperature rapid processings that have recently become popular. In order to compensate for such insufficient color forming properties, organic solvents such as benzyl alcohol, etc., have been added to a developing solution as an accelerator for color formation. However, such organic solvents for accelerating the color formation have several problems. For example, (1) since they are absorbed into emulsion layers during development, the amount thereof decreases in the developing solution, and thus the color formation becomes poor; (2) they are brought into the bleaching solution or bleach-fixing solution, and thus hinder desilvering or cause decrease in dye density; (3) they remain in the photographic material after processing and adversely affect the fastness of the dye images; and (4) they are mixed in processing wastes and cause undesirable increases in the biochemical oxygen demand (BOD) and chemical oxygen demand (COD) of the wastes.
For these reasons it has been eagerly desired to remove the organic solvents for accelerating color formation or reduce the amount thereof.
2-equivalent couplers of aryloxy releasing type are described, for example, in British Pat. No. 1,077,874, U.S. Pat. Nos. 3,419,391 and 3,476,563, Japanese Patent Application (OPI) No. 87650/75 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application"), etc. However, these 2-equivalent couplers of aryloxy releasing type are still insufficient in view of the color forming properties. Further, couplers containing a diffusion-resistant group having a p-hydroxyphenylsulfonyl group or a p-hydroxyphenylsulfinyl group at a terminus thereof as described in Japanese Patent Application (OPI) No. 42045/83 have been recently proposed. These couplers are recognized to have improved color forming properties in comparison with conventionally known couplers due to the functions of the diffusion-resistant group. However, the improvement is still not totally satisfactory, and they are disadvantageous because they have low solubility in organic solvents for dispersing couplers.